Simultaneous Optimization of Charge‐Carrier Balance and Luminous Efficacy in Highly Efficient White Polymer Light‐Emitting Devices

Zou, Jianhua; Wu, Hao; Lam, Ching Shan; Wang, Chuandao; Zhu, Jing; Zhong, Chengmei; Hu, Sujun; Ho, Cheuk Lam; Zhou, Guoquan; Wu, Hongbin; Choy, Wallace C. H.; Peng, Junbiao; Cao, Yong; Wong, Wai Yeung

doi:10.1002/adma.201101130

Cited by 207 publications

(93 citation statements)

References 32 publications

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“…Finally, we fabricated solution-processed multilayer white OLEDs by incorporating green-emitting Ir(ppy) 3 (0.2 wt%) and red-emitting tris(2-phenyl-1-quinoline)iridium(III) (Ir(phq) 3 ) (0.7 wt%) into the blue EML. Although the electroluminescence (EL) spectra of white OLEDs typically depend on current density (in other words, luminance) 4,6,19,[34][35][36][37] , the resulting solution-processed white OLED surprisingly showed no perceived change in the EL spectra under varying current density, as shown in Fig. 6a.…”

Section: Solvent Resistance Testmentioning

confidence: 92%

Solution-processed multilayer small-molecule light-emitting devices with high-efficiency white-light emission

et al. 2014

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Recent developments in the field of p-conjugated polymers have led to considerable improvements in the performance of solution-processed organic light-emitting devices (OLEDs). However, further improving efficiency is still required to compete with other traditional light sources. Here we demonstrate efficient solution-processed multilayer OLEDs using small molecules. On the basis of estimates from a solvent resistance test of small host molecules, we demonstrate that covalent dimerization or trimerization instead of polymerization can afford conventional small host molecules sufficient resistance to alcohols used for processing upper layers. This allows us to construct multilayer OLEDs through subsequent solution-processing steps, achieving record-high power efficiencies of 36, 52 and 34 lm W À 1 at 100 cd m À 2 for solution-processed blue, green and white OLEDs, respectively, with stable electroluminescence spectra under varying current density. We also show that the composition at the resulting interface of solution-processed layers is a critical factor in determining device performance.

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Section: Solvent Resistance Testmentioning

confidence: 92%

Solution-processed multilayer small-molecule light-emitting devices with high-efficiency white-light emission

et al. 2014

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“…There is no excimer or exciplex peak observed, indicating that electron and hole recombination were effectively confined into the EML. [36] Device B1 using ICz-PPI as the EML exhibited a maximum current efficiency (CE) of 2.35 cd A À 1 , a maximum power efficiency (PE) of 1.42 lm W À 1 and maximum external quantum efficiency (EQE) of 2.47 %, respectively. Device B2 using 2ICz-PPI as the EML showed slightly low performance (1.69 cd A À 1 , 1.13 lm W À 1 and 1.94 %) compared with device B1.…”

Section: Electroluminescence Propertiesmentioning

confidence: 99%

Versatile Host Materials for Highly‐Efficient Green, Red Phosphorescent and White Organic Light‐Emitting Diodes

et al. 2019

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To build up efficient host materials, two novel organic small molecules ICz‐PPI and 2ICz‐PPI were designed and synthesized, in which phenanthro[9,10‐d]imidazole (PI) is proposed as a potential luminophore with high stability, while the indolo[3,2,1‐jk]carbazole (ICz) has a high triplet energy and excellent thermal stability. Both exhibited weak intramolecular charge transfer, high decomposition temperature (Td) and high quantum yield. ICz‐PPI and 2ICz‐PPI can act as the emitting layer in non‐doped organic light‐emitting diodes (OLEDs), which achieved an external quantum efficiency (EQE) of 2.47 and 1.94 % with CIE coordinates of (0.153, 0.121) and (0.161, 0.102), respectively. In addition, the high triplet energy allows them to be used as hosts for phosphorescent OLEDs (PhOLEDs). Accordingly, high performance for green (62.5 cd A−1, 70.9 lm W−1, 17.8 %) and red (25.7 cd A−1, 26.9 lm W−1, 19.4 %) had been achieved from the ICz‐PPI‐based PhOLED. Particularly, the ICz‐PPI‐based red PhOLED showed surprisingly low roll‐off and maintained an EQE of 14.9 % at 10 000 cd m−2. Furthermore, an ICz‐PPI‐based white OLED (WOLED) exhibited warm white light (CIEx,y=(0.427, 0.468)) and high efficiencies with a CEmax of 31.8cd A−1, PEmax of 37.0lm W−1 and EQEmax of 14.4 %.

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“…Polymer OLEDs, or PLEDs offer potentially lower production cost and greater mechanical flexibility including elastomeric stretchability45678. The introduction of a phosphorescent dopant in the organic emissive material allows for harvesting both singlet and triplet exciton energy and can increase the internal quantum efficiency (η IQE ) of the OLEDs to 100%3.…”

mentioning

confidence: 99%

A Solution Processed Flexible Nanocomposite Electrode with Efficient Light Extraction for Organic Light Emitting Diodes

Liang

Chou

et al. 2014

Sci Rep

103

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Highly efficient organic light emitting diodes (OLEDs) based on multiple layers of vapor evaporated small molecules, indium tin oxide transparent electrode, and glass substrate have been extensively investigated and are being commercialized. The light extraction from the exciton radiative decay is limited to less than 30% due to plasmonic quenching on the metallic cathode and the waveguide in the multi-layer sandwich structure. Here we report a flexible nanocomposite electrode comprising single-walled carbon nanotubes and silver nanowires stacked and embedded in the surface of a polymer substrate. Nanoparticles of barium strontium titanate are dispersed within the substrate to enhance light extraction efficiency. Green polymer OLED (PLEDs) fabricated on the nanocomposite electrode exhibit a maximum current efficiency of 118 cd/A at 10,000 cd/m2 with the calculated external quantum efficiency being 38.9%. The efficiencies of white PLEDs are 46.7 cd/A and 30.5%, respectively. The devices can be bent to 3 mm radius repeatedly without significant loss of electroluminescent performance. The nanocomposite electrode could pave the way to high-efficiency flexible OLEDs with simplified device structure and low fabrication cost.

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Simultaneous Optimization of Charge‐Carrier Balance and Luminous Efficacy in Highly Efficient White Polymer Light‐Emitting Devices

Cited by 207 publications

References 32 publications

Solution-processed multilayer small-molecule light-emitting devices with high-efficiency white-light emission

Solution-processed multilayer small-molecule light-emitting devices with high-efficiency white-light emission

Versatile Host Materials for Highly‐Efficient Green, Red Phosphorescent and White Organic Light‐Emitting Diodes

A Solution Processed Flexible Nanocomposite Electrode with Efficient Light Extraction for Organic Light Emitting Diodes

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